Chapter 4 Compounds and
Their Bonds
Octet Rule
An octet
§  Is 8 valence electrons.
§  Is associated with the stability of the noble gases.
§  Helium (He) is stable with 2 valence electrons
(duet).
4.1
Octet Rule and Ions
Valence Electrons
2
He 1s2
Ne 1s2 2s2 2p6
8
Ar
8
1s2 2s2 2p6 3s2 3p6
Kr 1s2 2s2 2p63s2 3p6 4s2 3d10 4p6
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Ionic and Covalent Bonds
Metals Form Positive Ions
Atoms form octets
Metals form positive ions
§  By a loss of their valence electrons.
§  With the electron configuration of
the nearest noble gas.
§  That have fewer electrons than
protons.
Group 1A(1) metals ⎯→ ion 1+
Group 2A(2) metals ⎯→ ion 2+
Group 3A(3) metals ⎯→ ion 3+
§  To become more
stable.
§  By losing, gaining,
or sharing valence
electrons.
§  By forming ionic or
covalent bonds.
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Formation of a Sodium Ion, Na+
Charge of Sodium Ion, Na+
Sodium achieves an octet by losing its one valence
electron.
With the loss of its valence
electron, a sodium ion has a 1+
charge.
Sodium atom
11p+
11e0
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4
Sodium ion
11p+
10e1+
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1
Learning Check
Formation of Negative Ions
A. The number of valence electrons in aluminum is
1) 1e-
2) 2e-
In ionic compounds, nonmetals
§  Achieve an octet arrangement.
§  Gain electrons.
§  Form negatively charged ions with 3-, 2-, or 1charges.
3) 3e-
B. The change in electrons for octet requires a
1) loss of 3e-
2) gain of 3e-
3) gain of 5e-
C. The ionic charge of aluminum is
1) 3-
2) 5-
3) 3+
D. The symbol for the aluminum ion is
1) Al3+
2) Al3-
3) Al+
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Formation of a Chloride Ion, Cl-
Charge of a Chloride Ion, Cl-
Chlorine achieves an octet by adding an electron to
its valence electrons.
§  By gaining one electron, the
chloride ion has a -1 charge.
Chlorine atom
17p+
17e0
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Chloride ion
17p+
18e1-
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Ionic Charge from Group
Numbers
10
Some Typical Ionic Charges
TABLE 4.1
§  The charge of a positive ion is equal to its Group
number.
Group 1A(1) = 1+
Group 2A(2) = 2+
Group 3A(3) = 3+
§  The charge of a negative ion is obtained by
subtracting 8 or 18 from its Group number .
Group 6A(16) =
,I−
6-8 = 2-
or 16 - 18 = 2 -
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Chapter 4
Compounds and Their Bonds
Learning Check
A. Number of valence electrons in sulfur is
1) 4e2) 6e3) 8e-
4.2
Ionic Compounds
B. Change in electrons for octet requires a
1) loss of 2e2) gain of 2e- 3) gain of 4eC. Ionic charge of sulfur is
1) 2+
2) 2-
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Ionic Compounds
14
Salt is An Ionic Compound
Sodium chloride or table salt is an example of
an ionic compound.
Ionic compounds
§  Consist of positive and negative ions.
§  Have attractions called ionic bonds between
positively and negatively charged ions.
§  Have high melting and boiling points.
§  Are solid at room temperature.
15
Ionic Formulas
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Charge Balance for NaCl, Salt
In NaCl
§  A Na atom loses
its valence
electron.
§  A Cl atom gains an
electron.
§  The symbol of the
metal is written
first followed by
the symbol of the
nonmetal.
An ionic formula
§  Consists of positively and negatively charged ions.
§  Is neutral.
§  Has charge balance.
total positive charge = total negative charge
§  The symbol of the metal is written first followed by
the symbol of the nonmetal.
17
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Charge Balance In MgCl2
Charge Balance in Na2S
In MgCl2
§  A Mg atom loses
two valence
electrons.
§  Two Cl atoms
each gain one
electron.
§  Subscripts indicate
the number of ions
needed to give
charge balance.
In Na2S
§  Two Na atoms lose one valence electron each.
§  One S atom gains two electrons.
§  Subscripts show the number of ions needed to give
charge balance.
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Writing Ionic Formulas from
Charges
20
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Formula from Ionic Charges
Write the ionic formula of the compound with Ba2+
Charge balance is used to write the formula for
sodium nitride, a compound containing Na+ and N3−.
and Cl-.
§  Write the symbols of the ions.
3
Ba2+ Cl-
Na+
Na+ + N3−
Na+
=
3(+1) + 1(3-)
=
Na3N
§  Balance the charges.
Ba2+
0
ClCl-
two Cl- needed
§  Write the ionic formula using a subscript 2 for two
chloride ions that give charge balance.
BaCl2
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Chapter 4 Compounds and Their
Bonds
Learning Check
Select the correct formula for each of the following ionic
compounds
A. Na+ and S21) NaS
2) Na2S
3) NaS2
B. Al3+ and Cl1) AlCl3
2) AlCl
3) Al3Cl
C. Mg2+ and N31) MgN
2) Mg2N3
3) Mg3N2
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4.3
Naming and Writing Ionic Formulas
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4
Naming Ionic Compounds with
Two Elements
Charges of Representative
Elements
To name a compound
with two elements
§  Identify the cation
and anion.
§  Name the cation first
followed by the
name of the anion.
§  name = metal name
+ stem of nonmetal
name + -ide
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Names of Some Common Ions
26
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Learning Check
Complete the names of the following ions:
TABLE 4.3
Ba2+
_________
Al3+
__________
K+
_________
N3_________
O2__________
F_________
P3_________
S2__________
Cl_________
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Examples of Ionic Compounds
with Two Elements
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Learning Check
Write the names of the following compounds:
Formula
Ions
cation anion
Name
NaCl
Na+
Cl-
sodium chloride
K2S
K+
S2-
MgO
CaI2
Al2O3
1) CaO
___________
2) KBr
___________
potassium sulfide
3) Al2O3
___________
Mg2+ O2-
magnesium oxide
4) MgCl2
___________
Ca2+ I-
calcium iodide
Al3+
aluminum sulfide
S2-
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Learning Check
Transition Metals form Positive
Ions
Write the formulas and names for compounds of
the following ions:
Br−
S2−
N3−
Most transition metals and Group 4(14) metals
§  Form 2 or more positive ions.
§  Zn2+, Ag+, and Cd2+ form only one ion.
Na+
Al3+
31
Metals that form more than One
Cation
Pb2+
lead(II)
Pb4+
lead(IV)
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Naming Variable Charge Metals
The name of metals with two or more positive ions
(cations) use a Roman numeral to identify ionic charge.
Lead
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Transition metals that form two different ions use a
Roman numeral after the name of the metal ion to
indicate the charge.
33
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Naming FeCl2
Learning Check
STEP 1 Determine the charge of the cation from the
anion.
Fe ion + 2 Cl- = Fe ion + 2- = 0
Fe ion = 2+
STEP 2 Name the cation by the element name and use
a Roman numeral to show its charge.
Fe2+ = iron(II)
STEP 3 Write the anion with an ide ending. chloride
STEP 4 Name cation first. iron(II) chloride
Select the correct name for each.
A. Fe2S3
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1) iron sulfide
2) iron(II) sulfide
3) iron (III) sulfide
B. CuO
1) copper oxide
2) copper(I) oxide
3) copper (II) oxide
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Writing Formulas
Writing Formulas
Write a formula for potassium sulfide.
STEP 1 Identify the cation and anion.
potassium = K+
sulfide
= S2−
STEP 2 Balance the charges.
K+
S2−
K+
2(1+) + 1(2-) = 0
Write a formula for iron(III) chloride.
STEP 1 Identify the cation and anion.
iron (III) = Fe3+ (III = charge of 3+)
chloride = Cl−
STEP 2 Balance the charges.
Fe3+ Cl−
Cl−
Cl−
(3+) + 3(1-) = 0
STEP 3 Write the cation first.
1 Fe3+ and 3Cl− = FeCl3
STEP 3 Write the cation first.
2K+ and 1S2− = K2S1 = K2S
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Chapter 4 Compounds and Their
Bonds
Learning Check
4.4
Polyatomic Ions
The correct formula for each of the following is:
A. Copper (I) nitride
1) CuN
38
2) CuN3
3) Cu3N
2) PbO
3) Pb2O4
B. Lead (IV) oxide
1) PbO2
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Some Compounds with Polyatomic
Ions
Polyatomic Ions
A polyatomic ion
§  Is a group of atoms.
§  Has an overall ionic charge.
Some examples of polyatomic ions are
NH4+
ammonium
OH−
hydroxide
NO3
nitrate
NO2−
nitrite
−
CO32−
HCO3−
carbonate
PO43− phosphate
hydrogen carbonate
(bicarbonate)
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Names and Formulas of Common
Polyatomic Ions
Some Names of Polyatomic Ions
The names of common polyatomic anions
§  End in ate.
NO3− nitrate
PO43−
phosphate
§  With one oxygen less end in ite.
NO2− nitrite
PO33−
phosphite
§  With hydrogen attached use prefix hydrogen (or bi).
HCO3−
hydrogen carbonate (bicarbonate)
HSO3−
hydrogen sulfite
(bisulfite)
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Names and Formulas of Common
Polyatomic Ions
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Naming Compounds with
Polyatomic Ions
§  The positive ion is named first followed by the name
of the polyatomic ion.
NaNO3
sodium nitrate
K2SO4
potassium sulfate
Fe(HCO3)3
iron(III) bicarbonate
or iron(III) hydrogen carbonate
(NH4)3PO3
ammonium phosphite
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Some Compounds with Polyatomic
Ions
46
Learning Check
Match each formula with the correct name:
TABLE 4.8
A. MgS
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1) magnesium sulfite
MgSO3
2) magnesium sulfate
MgSO4
3) magnesium sulfide
B. Ca(ClO3)2
1) calcium chlorate
CaCl2
2) calcium chlorite
Ca(ClO2)2
3) calcium chloride
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Learning Check
Writing Formulas with Polyatomic
Ions
Name each of the following compounds:
The formula of an ionic compound
A.
Mg(NO3)2
§  Containing a polyatomic ion must have a charge
balance that equals zero(0).
B.
Cu(ClO3)2
§ 
C. PbO2
→
NaNO3
§  With two or more polyatomic ions has the
polyatomic ions in parentheses.
D. Fe2(SO4)3
E.
Na+ and NO3−
Ba3(PO3)2
Mg2+ and 2NO3− →
Mg(NO3)2
subscript 2 for charge balance
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Learning Check
Learning Check
Select the correct formula for each:
Write the correct formula for each:
A. potassium bromate
B. calcium carbonate
C. sodium phosphate
D. iron(III) oxide
E. iron (II) nitrite
A. aluminum nitrate
1) AlNO3
2) Al(NO)3
3) Al(NO3)3
2) Cu(NO3)2
3) Cu2(NO3)
B. copper(II) nitrate
1) CuNO3
C. iron (III) hydroxide
1) FeOH
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2) FeOH3
3) Fe(OH)3
2) Sn(OH)2
3) Sn4(OH)
D. tin(IV) hydroxide
1) Sn(OH)4
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Learning Check
Learning Check
Name the following compounds:
Write the formulas for the following:
A. Ca3(PO4)2
A. calcium nitrate
B. FeBr3
B. iron(II) hydroxide
C. Al2S3
C. aluminum carbonate
D. Zn(NO2)2
D. copper(II) bromide
E. NaHCO3
E. lithium phosphate
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